Solid Motion Research Articles

Charge transfer excitons in a donor–acceptor amphidynamic crystal: the role of dipole orientational order

Large amplitude motions in molecular solids are responsible for anomalous electrical characteristics in amphidynamic crystals. Here we explore the implications for charge transfer excitons photophysics.

The Development of the Method and Determination of the Relative Abrasiveness of Bulk Substances

This article touches upon the preliminary results of determining the coefficient of relative abrasiveness of various bulk materials. An experimental setup for determining the abrasiveness of various bulk materials is described, which makes it possible to set the abrasiveness of a material with different physical properties and fractions of the frayed material.It is noted that during experiments it is necessary to ensure the stability of fractions. It is scheduled to determine the critical speed of movement of bulk solids, which eliminates the change in fraction size through grinding when the test material is abraded by samples. It is emphasized that the abrasiveness of the test material is determined on the material recognized as a reference.

Numerical identification of critical erosion prone areas in tube heat exchangers

The failure of tube heat exchangers is an acute problem in industry and, in most cases, is due to the solid particle erosion of a few tubes. Identifying the critical erosion surfaces and thereafter changing the particle impingement pattern on the surfaces is one of the solutions to increase the lifetime of heat exchangers. In this work the fluid flow, solid particle motion and metal erosion of different two-pass copper-tube heat exchangers were simulated with a refined model and the sophisticated RANS-SST approach. The results showed the importance of the model in capturing the asymmetrical flow, uneven fluid distribution through tube bundle and other flow features for better erosion prediction. The erosion characteristics of three heat exchangers were compared to evaluate their structure with respect to producing low erosion. The simulations provided basic data for identifying the critical areas and damage locations of each heat exchanger. It was found that the particle separation in the inlet header altered the critical erosion locations but did not significantly affect the erosion rate. Theerosion rates at critical areas were also predicted. The results can be applied for predicting the service life and improving the structure of tube heat exchangers.

Расчетно-теоретическое исследование характеристик течения двухфазного потока в пескоструйном аппарате

The paper considers the possibility of conversion applying of a rocket engine as a sandblasting machine for thermo-abrasive treatment. The higher performance characteristics of a treated surface can be achieved through the exposure of the high-temperature two-phase flow accelerated in the device nozzle barrel on the object. The ejection feed of granular abrasive substances determines the relative structural simplicity of the device structure. The authors prove the efficiency of such a device using the gas-dynamic process modeling in the CFD software package, the calculations of which are based on combined equations including the key parameters of both the carrier gas and the solid phase particles. The process modeling considers the influence of the geometry and the specifics equal to the real operating prototype. During further analysis, to determine the optimal mode, the authors investigated the influence of various border conditions on the supersonic two-phase flow. The study considers the mutual influence of gas flow and abrasive solid particles starting from the powder delivery section to the nozzle outlet section. The study presents the comparison of temperature and pressure fields depending on the input values, as well as the fluid velocity fields based on these values. The authors carried out the analysis of the dependence of solid particle motion speed on the coordinate at various initial data of temperature and pressure. The study pays special attention to the consideration of the impact of the k -phase particle size on the speed parameters. During the study, the authors identified the main methods of device adjustment to achieve the required mode parameters. As a result of the analysis, the paper concludes on the efficiency and competitive ability of the thermo-abrasive treatment method under the study.

Exploration and Practice of Solid State Physics Teaching Reform

Solid state physics is to study the structure and composition of the solid par-ticle interaction and movement rules, and to elucidate the relationship between its structure and properties and its use of the subject, is the theoretical basis of new materi...

Computational Fluid Dynamics of System Hydrodynamics and Erosion Behavior in Internally Circulating Fluidized Bed Reactor with Inserting Pipe

Internally circulating fluidized bed reactor (ICFB) is the system with combining the function of reactor, cyclones and loop seal of a conventional circulating fluidized bed reactor (CFB) into a single reactor column. In this type of reactor, the reactor column is separated into two sections (riser and downer) by baffles and is linked together via connecting ports. This system is then considered as compact operation when comparing with the conventional CFB reactor. However, the simplicity of the ICFB reactor is trade-off with a gas leakage which takes place between the two sections through the connecting ports. In addition, the solid particle movement inside the system can cause the erosion on the inserting pipes which are used for heating or cooling this ICFB reactor column. In this study, the system hydrodynamics and erosion behavior inside ICFB reactor with inserting pipe were investigated by computational fluid dynamics (CFD) using two-dimensional Eulerian-Eulerian model. The adjusted Gidaspow drag model was applied to compute the interaction between the gas and solid particle phases. Then, the system hydrodynamics was obtained and the wall shear stress was calculated in the existent of the erosion at the surface region of the inserting pipes. The results from this simulation were used to design the inserting pipe arrangement inside this ICFB reactor.

Комбинированный алгоритм вычисления расстояния со знаком для задач численного моделирования физических процессов и визуализации движения твердых тел

Комбинированный алгоритм вычисления расстояния со знаком для задач численного моделирования физических процессов и визуализации движения твердых тел

An immersed phase field fracture model in fluid-infiltrating porous media with evolving Beavers-Joseph-Saffman condition

This study presents a phase field model for brittle fracture in fluid-infiltrating vuggy porous media. While the state-of-the-art in hydraulic phase field fracture considers Darcian fracture flow with enhanced permeability along the crack, in this study, the phase field not only acts as a damage variable that provides diffuse representation of cracks or cavities, but also acts as an indicator function that separates the domain into two regions where fluid flows are governed by Stokes and Darcy equations, respectively. Since the phase field and its gradient can be respectively regarded as smooth approximations of the Heaviside function and Dirac delta function, our new approach is capable of imposing interfacial transmissibility conditions without explicit interface parametrizations. In addition, the interaction between solid and fluid constituents is modeled by adopting the concept of mixture theory, where the fluid velocities in Stokes and Darcy regions are considered as relative measures compared to the solid motion. This model is particularly attractive for coupled flow analysis in geological materials with complex microstructures undergoing brittle fracture often encountered in energy geotechnics problems, since it completely eliminates the needs to generate specific enrichment function, integration scheme, or meshing algorithm tailored for complex geological features.

A resolved CFDEM method for the interaction between the fluid and the discontinuous solids with large movement

SummaryA novel resolved combination of the computational fluid dynamics and the discrete element method (CFDEM) is proposed for the simulation of the strong coupling between the fluid and the discontinuous solids with large movement. The fluid flow governed by the full Navier‐Stokes equations is simulated using fixed grids based on the Eulerian framework, whereas the motion of the discontinuous solids is modeled by the discrete element method using the Lagrangian description. The key challenge, namely, the representation of the moving interfaces between the fluid and the solids in different frameworks, is handled by the immersed boundary method. Meanwhile, the governing equations of the coupled system are solved by the partitioned method in an iterative way to achieve a strong coupling effect. The breakthrough of the proposed resolved CFDEM method lies in the calculation of the fluid flow in fixed grids with high resolution, along with an accurate simulation of the interaction between the fluid and the discontinuous solids with arbitrary shapes and large movement. The reliability and the accuracy of the new method are validated by calculating several well‐known benchmark examples. Good agreements are achieved between the present and the known results.

A conjugate heat transfer model for unconstrained melting of macroencapsulated phase change materials subjected to external convection

A new conjugate heat transfer model for unconstrained melting of macroencapsulated phase change material subjected to external convection is presented. Flow and heat transfer processes are modeled for the phase change material, the capsule wall and the external heat transfer fluid. The solvers for each region operate in a segregated and sequential manner and are coupled by mixed thermal boundary conditions. For the description of the solid body motion in unconstrained melting, the enthalpy-porosity method is modified. The solid body surface is reconstructed from the liquid volume fraction field for every time step by a triangulated isosurface using a marching tetrahedra technique. Based on computation of the forces exerted on the solid, the motion of the solid is determined iteratively in a strong coupling between solid velocity and pressure. The new conjugate heat transfer solver is utilized to simulate the commonly experimentally and numerically investigated scenario of a spherically encapsulated phase change material immersed in a water bath. The coupled flow and heat transfer is investigated for a natural convection dominated mixed convection problem with a Richardson number of 50 · 103 and Stefan numbers of 0.075, 0.1, 0.15, 0.2 and 0.25. Contrary to the commonly made assumption, the resulting capsule wall temperature is transient and highly non-uniform. The differences in melting times range from 50.7 to 67.5% between the consideration of external heat transfer and the assumption of constant uniform wall temperatures.

Numerical analysis of wave-induced current within the inhomogeneous coral reef using a refined SPH model

The effects of reef permeability on the spatial distributions of wave-induced current inside and outside the inhomogeneous coral reef body are investigated using an improved weakly compressible smoothed particle hydrodynamic (WCSPH) mixture model. The governing equations are formulated based on the two-phase mixture theory without considering the solid phase motion in terms of the intrinsic velocity and fluid density. The developed WCSPH mixture model is firstly validated by comparing the predicted results with the corresponding available data for Darcy seepage flow in a U-tube with permeable soil, wave damping over a permeable seabed and wave transformation over a permeable reef. The validated model is then applied to study the spatial distributions of wave-induced current inside and outside the permeable reef body with different porosity and porous layer thickness. Finally, a parametric study is carried out to investigate the effects of different porosity distribution types on wave-induced currents.

The grinding bodies movement dynamics study in a ball mill equipped with energy-exchanging devices

The article deals with the issues related to energy saving during grinding in a ball mill equipped with energy exchange devices, pre-milled in a press-roller grinder. The bulk solids movement analysis in a ball mill at different locations in the energy exchange devices drum is presented.

Transport of Solid Particles with Fluid Flow in Rotating Pipes

Abstract The article addresses the recent problem of borehole lifting of oil containing sand solids. The presence of sand in oil produced results in a reduced operating life of downhole equipment. The problem of preventing sanding up and sand formation in pumping equipment may be solved and stable sand production may be ensured by producing oil using borehole screw pumps with a surface-type drive, in which the screw is rotated by rotating hollow rods. Rotating hollow rods improve carry-over of sand particles to the surface with rotational oil flow by imparting additional momentum to these particles. Rotational variables of the pipe (cylinder) that enables transport of solids are set only for the air flow moving in a horizontal pipe (cylinder). The purpose of the study is to establish pipe rotational variables in directional wells that enable stable sand transport with fluid flow. Work results have been obtained from numerical studies using the differential equation system and rules of theoretical solid movement, computer simulation and experimental results processing at a laboratory facility. Theoretical study results have been acknowledged by experimental studies. The work establishes the criteria that allow defining the speed range of directional hollow rods that enables carry-over of solids to the surface with fluid flow. Study results may be used to produce oil with submersible screw pumps with a surface-type drive that use hollow sucker rods for pump down.

A Simple and Easy Movie Recommendation System

Proposal frameworks have gotten common lately as they managing the data over-burden issue by recommending clients the most pertinent items from an enormous measure of data. For media item, online collective motion picture suggestions make endeavors to help clients to get to their favored films by catching exactly comparative neighbors among clients or motion pictures from their verifiable basic evaluations. In any case, because of the data meagerly, neighbor choosing is getting progressively troublesome with the quick expanding of motion pictures and clients. In this paper, a half and half model-based motion picture suggestion framework which uses the improved K-implies bunching combined with genetic algorithms (GA) to segment changed client space is proposed. It utilizes principal component analysis (PCA) data decrease method to thick the motion picture populace space which could lessen the calculation unpredictability in savvy film suggestion too. The examination results on Movielens dataset demonstrate that the proposed methodology can give superior as far as accuracy, and create progressively solid and customized motion picture suggestions when contrasted and the current techniques

Technical feasibility analysis of a linear particle solar receiver

This work proposes a new particle receiver for Concentrating Solar Technology (CST) that employs air and particles as heat transfer fluid (HTF). The novel Linear Particle Solar Receiver (LPSR) is located at the ground level receiving the concentrated solar energy linearly from the top. This receiver is formed by several fluidized beds connected consecutively allowing the horizontal movement of solids and the linear absorption of solar energy. A new solar field is proposed and analyzed to redirect the concentrated solar energy towards the receiver linearly.The optic analysis of a linear beam-down system is carried out using a ray-tracing software. Then, the performance of a linear particle solar receiver is analyzed considering target temperatures of 200 °C, 400 °C, 600 °C and 800 °C to reproduce CST integration with medium and high temperature process heat, Rankine power generation and supercritical CO2 (sCO2) cycles, respectively. The temperature of the hot streams of air and sand are calculated considering the heat losses from the receiver and the compressor parasitic consumption. The procedure to determine the optimum design is shown studying one line as a function of the target temperature. For instance, a sand mass flow of 1.75 kg/s in a receiver of 0.5 m width and a secondary reflector eccentricity of 0.8, can be heated up to 600 °C in a length of 280 m, showing a solar field efficiency of 40.25% and a receiver thermal efficiency of 80%.

Phase-field lattice Boltzmann model for dendrites growing and moving in melt flow

The phase-field and lattice Boltzmann methods have been combined to simulate the growth of solid particles moving in melt flow. To handle mobile particles, an overlapping multigrid scheme was developed, in which each individual particle has its own moving grid, with local fields attached to it. Using this approach we were able to simulate simultaneous binary solidification, solute diffusion, melt flow, solid motion, the effect of gravity, and collision of the particles. The method has been applied for describing two possible modes of columnar to equiaxed transition in the Al–Ti system.

A Kinematic Controller for Liquid Pouring between Vessels Modelled with Smoothed Particle Hydrodynamics

In robotics, the task of pouring liquids into vessels in non-structured or domestic spaces is an open field of study. A real time, fluid dynamic simulation, based on smoothed particle hydrodynamics (SPH), together with solid motion kinematics, allow for a closed loop control of pouring. In the first place, a control criterion related with the behavior of the liquid free surface is established to handle sloshing, especially in the initial phase of pouring to prevent liquid adhesion over the vessel rim. A 2-D, free surface SPH simulation is implemented on a graphic processing unit (GPU) to predict the liquid motion with real-time capability. The pouring vessel has a single degree of freedom of rotation, while the catching vessel has a single degree of freedom of translation, and the control loop handles the tilting angle of the pouring vessel. In this work, a two-stage pouring method is proposed, differentiating an initial phase where sloshing is particularly relevant, and a nearly constant outflow phase. For control purposes, the free outflow trajectory was simplified and modelled as a free falling solid with an initial velocity at the vessel crest, as calculated by the SPH simulation. As the first stage of pouring is more delicate, a novel slosh induction method (SIM) is proposed to overcome spilling issues during initial tilting in full filled vessels. Both robotic control and fluid modelling showed good results at multiples initial vessel filling heights.

Experimental Study of Solids Motion in an 18 m Gas–Solids Circulating Fluidized Bed with High Solids Flux

A comprehensive experimental study of solids motion is conducted in an 18-m high circulating fluidized bed with extremely high solids circulating rate (Gs) up to 1000 kg/(m2 s), which is never achieved in such a tall riser in previous researches. The axial distributions of particle velocity show exponential types and slight changes in the fully-developed zone with Gs higher than 400 kg/(m2 s). The radial profiles of particle velocity are the parabolic shapes and become steeper with increasing Gs. The development of gas-solids flow structure becomes slower with increasing Gs or decreasing Ug. When Gs reaches 800 kg/(m2 s), the full development is achieved until to the axial height higher than 12 m. Better correlations between the local particle velocity and solids holdup and less down-flowing particles indicate better reactor performance with the reducing solids back-mixing and uniform residence times at extremely high Gs.

Numerical simulation of particle-laden flow in an industrial wastewater sedimentation tank

The wastewater of steel production factories consists of a large amount of very small metal particles. The metal particles in this wastewater enter a large sedimentation tank and are deposited on the floor of it. In this study, the turbulence particle-laden flow in the sedimentation tank of a steel rolling company is investigated. The Reynolds Averaged Navier–Stokes equations are solved with SST k-ω and standard k-e turbulence models. Two-phase flow simulation is performed using the discrete phase model. Particle structure is determined by a scanning electron microscope. Based on the range of particle size, the particles are divided into 13 classes. Each class is injected into the continuous phase and then tracked. In order to evaluate the results, the settling efficiency is determined by sampling the input and output wastewater. This efficiency is compared with the results of numerical simulation. The pattern of solid particle motion shows that the nature of particle motion is three-dimensional. Particle tracking indicates that the settling efficiency increases with increasing the particle diameter. The streamlines show that a large and strong eddy is created in the sedimentation tank. This eddy is so strong that acts as a dead zone and reduces the efficiency of tank. In the following, the effect of environmental temperature on the efficiency of sedimentation tank is investigated. Results show that with increasing the temperature of the wastewater, the efficiency of settling tank increases.

Nanofluidic Behavior at the Fluid-Solid Interface

Abstract The confinement and nature of complexity at the fluid-solid interface pose significant challenges for studying the nanofluidic behavior. Here, we report an approach to probe the rheological performance of three media through dynamic interaction with a harmonic oscillator. A prototype device is developed that is able to vibrate in the range up to hundreds of hertz. Results show that the interfacial viscosity was similar to that of its bulk in terms of amplitude and frequency. However, an additional phase lag appeared when the amplitude was small, and its responsive curve exhibited distortion around the natural frequency. Theoretical analysis indicated that this might be due to fluid memory because the fluid response to the solid motion is not instantaneous. The approach reported here has potential to lead toward new ways of studying dynamic properties of fluid-solid interfaces.